Chemistry is an experiment based science

Chemistry is an experiment-based natural science, which mainly studies the composition, structure, properties and changes of matter.

Candles and their burning **.

In the experiment, we should pay attention to the properties of the substance, such as color, odor, state, hardness, density, melting point, boiling point, etc.; Second, we should pay attention to the changes of the substance, such as whether the paraffin wax melts when burned; Third, we should pay attention to the change process of matter and its phenomena, such as luminescence, heat release, gas generation, etc. Compare your observations of candle burning with the description below. Before ignition:

The candle is composed of paraffin wax and cotton wicks, ordinary candles are cylindrical solid, milky white (special-purpose candles are made of different colors and shapes due to the addition of ingredients), the feel is slippery, there is a slight smell, the texture is softer, it is insoluble in water, and the density is smaller than water. When burning: A lit candle can burn continuously, and the candle slowly becomes shorter.

If the candle is blown or heated unevenly, the liquid stored in the groove will flow down the candle body and gradually solidify and adhere to the candle body when cold. The flame of the candle is divided into three layers: outer flame, inner flame and flame core, and the outer flame is in full contact with the air, and the temperature is the highest. When the candle is burning, cover the flame with a dry and cold beaker, find that there is a water mist on the inner wall of the beaker, remove the beaker, quickly pour a small amount of clarified lime water, shake, the clarified lime water becomes turbid, indicating that there is water and carbon dioxide generation after the candle burns.

After extinguishing: When the candle is just extinguished, a wisp of white smoke floats out of the wick, igniting the white smoke, and the flame will follow the white smoke to relight the candle.

That's right, you know, what do you want to ask?!

Answer: Because many major discoveries and research results in chemistry are obtained through experiments, in addition, an important way to learn chemistry is experiments, through experiments and observation, recording and analysis of experimental phenomena, you can discover and verify chemical principles, learn scientific methods and obtain chemical knowledge

Reason: From ancient alchemy to today's chemical scientific research, all the discoveries or achievements made during this period have not been obtained or tested through experiments, that is, chemistry is the basis of all chemical achievements; In addition, when we study chemistry today, we must also discover and verify some principles through experiments, gain knowledge in scientific experiments, and consolidate knowledge.

Chemistry is first and foremost an experimental discipline and then a theoretical subject.

Chemistry is a basic natural discipline that studies the composition, structure, properties and changes of matter.

These changes need to be confirmed by experiments, the transformation of one thing into another, the migration of electrons, the breaking and regeneration of various chemical bonds, and the transformation of decay into magic, but carbon is still that carbon, oxygen is still that oxygen, nitrogen is still that nitrogen, it is just a transformation of the structure.

Chemistry is an experiment-based science

Because chemistry does a lot of experimentation.

Chemistry is a kind of natural science, which studies the composition, properties, structure and change laws of matter at the molecular and atomic levels. The science of creating new matter. The world is composed of matter, and chemistry is one of the main methods and means used by human beings to understand and transform the material world. It is a discipline with a long history and vitality, and its achievements are an important symbol of social civilization.

These are all theories that have been derived through experiments.

Chemistry is actually not difficult, as long as you put your mind to it, you can learn it well.

First of all, it's a very comprehensive subject and it's a lot of fun.

Chemical formulas, chemical equations, concepts, experimental phenomena can be solved in the form of memorization in the liberal arts - this is dead knowledge, you must work hard to memorize these, memorize these well, and you will have a foundation in the future.

You can use the divergent thinking of science to solve experimental problems, as well as comprehensive problems. It is closely related to mathematics and physics, but it is simpler than mathematical physics. For example, experiments, experiments are particularly fun, as long as you watch the class carefully, even if you don't memorize the experiment, you will remember it during the exam.

And so on, and so on.

In fact, the most important thing is interest, as a new subject, as long as you are serious, it is impossible to learn badly. If you are interested in this subject, you will naturally learn it well

Highly recommended] A summary of the chemical equation of the first year of high school.

In secondary school, it is true ... At the university, only analytical chemistry is the experimental basis, and the rest is theoretical. In middle school, it's not difficult to learn, but it's definitely not as easy as you think.

(1) A The principle of fire extinguishing is to isolate the air or reduce the temperature, and if the burning alcohol lamp accidentally overturns the fire, it should be immediately covered with a wet cloth to extinguish it, so it is correct to isolate the air and achieve the purpose of extinguishing the fire;

b If the Erlenmeyer flask for titration is washed with a standard solution, the measurement result will be too large, so it is wrong;

c. When measuring the pH of the solution, if the pH test paper is wetted first, resulting in a decrease in the concentration of the solution, the measurement result will produce an error, so it is wrong;

d Ethylene and sulfur dioxide both react with bromine, ethylene undergoes addition reaction, sulfur dioxide undergoes redox reaction, so sulfur dioxide in ethylene cannot be removed with bromine water, sulfur dioxide in ethylene should be removed with NaOH solution, so it is wrong;

e When separating liquid, the lower liquid in the separating funnel flows out from the lower mouth, and in order to prevent impurities, the upper liquid is poured out from the upper mouth, so it is correct;

f Sulfur is insoluble in water, slightly soluble in alcohol, soluble in carbon disulfide, soluble in hot alkali, so it can be removed with hot alkali, so it is correct;

g The graduated cylinder can only measure the solution, but cannot prepare the solution or dilute the solution, so it is wrong;

h Concentrated alkali is corrosive, accidentally dip the concentrated alkali solution on the **, immediately rinse with a large amount of water, and then apply boric acid solution, so it is correct;

Therefore, AEFH is chosen;

2) A Drop solution to the test tube should be suspended, otherwise the dropper will be polluted, so it is wrong;

b. When heating solid drugs, the mouth of the test tube should be lower than that of the test tube, otherwise the water generated by the condensation of water vapor will reflux and burst the test tube, so it is wrong;

c. The air duct in the gas scrubbing device follows the principle of "long in and short out", otherwise the lotion will be discharged from the gas scrubbing cylinder, so it is wrong;

d When preparing ethyl acetate, the trachea can not be extended into the saturated sodium carbonate solution, otherwise, it is easy to produce suction, so it is correct;

Therefore, choose D; 3) The instrument is a graduated cylinder, and its inductance is, so the volume of the solution is; Use one of the above four instruments to measure the volume of a liquid, and the upward value is greater than the head-up value, indicating that the large value on the instrument is below, and only the burette meets the conditions, so choose c, so the answer is: ; c．

(1) a, remove combustibles, isolate oxygen or reduce the temperature below the ignition point can extinguish the fire, wet cloth cover can not only reduce the temperature below the ignition point but also isolate the air, so a is correct;

B. Dilute acid accidentally sticks to clothes or **, it should be wiped off with a rag first, and then rinsed with water, concentrated NaOH has strong corrosiveness, so it cannot be cleaned with concentrated NaOH, so B is wrong;

c. When weighing the quality of the item with a tray balance, the item should be placed on the left plate, so C is wrong;

d The remaining drugs in the experiment can neither be put back into the original bottle, nor can they be discarded at will, let alone taken out of the laboratory, and should be placed in the designated container, so D is wrong;

e Impure flammable gas may produce ** when burning, so the gas must be tested for purity before igniting the flammable gas, so e is correct;

f The separating funnel can be used to hold liquid, and there is a piston, and it must be checked for water leakage when using, so f is correct;

So the answer is: AEF;

2) 1 The lumpy solid does not slide into the test tube along the inclined test tube wall, and the consequence is to break the test tube, so the answer is: the bottom of the test tube is easy to rupture;

2. When measuring the liquid with a graduated cylinder, the line of sight should be level with the lowest part of the liquid concave surface in the measuring cylinder; Looking up at the volume of liquid in the measuring cylinder, the reading is smaller than the actual liquid volume, so the answer is: the reading is low;

3 Slowly pour concentrated sulfuric acid into the beaker containing water along the inner wall of the beaker, and stir continuously with a glass rod to make the heating even, and the water will splash when poured into the concentrated sulfuric acid, so the answer is: the water on the surface of the liquid in the graduated cylinder will splash

1) The instrument that can be heated directly is the test tube in the figure;

The dropper used to aspirate and drop a small amount of liquid is the dropper in the figure;

The instrument that needs to be padded with an asbestos mesh for heating is the beaker in the figure;

When doing experiments on the combustion of magnesium belts in air, the instrument that clamps the magnesium belts is crucible forceps

x) When measuring the volume of liquid with a graduated cylinder, the line of sight should be parallel to the lowest part of the concave liquid surface;

3) A When the alcohol lamp is knocked down and the alcohol burns, immediately cover it with a wet rag, which can isolate the air and extinguish the fire, so it is correct;

b. After the experiment is completed, if there is excess medicine, the drug can be put back into the original reagent bottle, which will contaminate the drug, so it is wrong;

c. It is found that the top of the wick of the alcohol lamp has been burned, and the alcohol lamp is not easy to ignite, so the burnt part should be cut off, so it is correct;

d The vegetable cellar that has not been opened for a long time contains more carbon oxide, so it is correct to do a light experiment before entering the vegetable cellar that has not been opened for a long time

Therefore, choose B

Therefore, the teaching of chemistry, as a knowledge of chemical science, must also be based on experiments Chemical experiments are an important way to learn chemistry

So the answer is: chemistry experiments